Method and apparatus for measurement reference signal

ABSTRACT

Methods and apparatuses for reference signal measurement. A user equipment (UE) includes a transceiver and a processor operably connected to the transceiver. The transceiver is configured to receive reference signal (RS) resource configuration information and at least two RSs. The processor is configured to measure at least one of the at least two RSs. A first RS of the at least two RSs is non-UE-specifically configured and a second RS of the at least two RSs is UE-specifically configured.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.15/437,413, filed Feb. 20, 2017, which claims priority under 35 U.S.C. §119(e) to: U.S. Provisional Patent Application No. 62/298,643 filed Feb.23, 2016; U.S. Provisional Patent Application No. 62/303,779 filed Mar.4, 2016; U.S. Provisional Patent Application No. 62/358,225 filed Jul.5, 2016; U.S. Provisional Patent Application No. 62/349,361 filed Jun.13, 2016; U.S. Provisional Patent Application No. 62/417,616 filed Nov.4, 2016; and U.S. Provisional Patent Application No. 62/445,993 filedJan. 13, 2017. The contents of the above-identified patent documents areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to transmission of measurementreference signals. Such reference signals can be used for measuringchannel state information (CSI) or other channel-quality-relatedquantities such as reference signal received power (RSRP).

BACKGROUND

Wireless communication has been one of the most successful innovationsin modern history. The demand of wireless data traffic is rapidlyincreasing due to the growing popularity among consumers and businessesof smart phones and other mobile data devices, such as tablets, “notepad” computers, net books, eBook readers, and machine type of devices.To meet the high growth in mobile data traffic and support newapplications and deployments, improvements in radio interface efficiencyand coverage is of paramount importance.

A mobile device or user equipment can measure the quality of thedownlink channel and report this quality to a base station so that adetermination can be made regarding whether or not various parametersshould be adjusted during communication with the mobile device. Existingchannel quality reporting processes in wireless communications systemsdo not sufficiently accommodate reporting of channel state informationassociated with large, two dimensional array transmit antennas or, ingeneral, antenna array geometry which accommodates a large number ofantenna elements.

SUMMARY

Various embodiments of the present disclosure provide methods andapparatuses for CSI reporting.

In one embodiment, a user equipment (UE) is provided. The UE includes atransceiver and a processor operably connected to the transceiver. Thetransceiver is configured to receive reference signal (RS) resourceconfiguration information and at least two RSs. The processor isconfigured to measure at least one of the at least two RSs. A first RSof the at least two RSs is non-UE-specifically configured and a secondRS of the at least two RSs is UE-specifically configured.

In another embodiment, a base station (BS) is provided. The BS includesa processor and a transceiver operably connected to the processor. Thetransceiver is configured to generate RS resource configurationinformation for a UE and at least two RSs for the UE. The transceiver isconfigured to transmit, to the UE, the RS resource configurationinformation and the at least two RSs. A first RS of the at least two RSsis non-UE-specifically configured and a second RS of the at least twoRSs is UE-specifically configured.

In another embodiment, a method for operating a UE is provided. Themethod includes receiving, by the UE, RS resource configurationinformation and at least two RSs and measuring at least one of the atleast two RSs. A first RS of the at least two RSs is non-UE-specificallyconfigured and a second RS of the at least two RSs is UE-specificallyconfigured.

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesBeyond 4th-Generation (4G) communication system such as Long TermEvolution (LTE).

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it can beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller can beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllercan be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items can be used,and only one item in the list can be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to variousembodiments of the present disclosure;

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to various embodiments of the present disclosure;

FIG. 3A illustrates an example user equipment according to variousembodiments of the present disclosure;

FIG. 3B illustrates an example enhanced NodeB (eNB) according to variousembodiments of the present disclosure;

FIG. 4 illustrates an example beamforming architecture wherein oneCSI-RS port is mapped onto a large number of analog-controlled antennaelements according to embodiments of this disclosure;

FIG. 5 illustrates an example two-level CSI-RS design which includes twocoverage CSI-RS settings and two UE-specific CSI-RS settings within thefirst coverage CSI-RS according to embodiments of this disclosure;

FIG. 6 illustrates an example two-level CSI-RS design which includes sixcoverage CSI-RS settings and a UE-specific CSI-RS setting within thefirst coverage CSI-RS according to embodiments of this disclosure;

FIG. 7 illustrates an example three-level CSI-RS design according toembodiments of this disclosure;

FIG. 8 illustrates three examples of CSI-RS configurations for two-levelCSI-RS according to embodiments of this disclosure;

FIG. 9 illustrates an example of aperiodic CSI-RS which includes eNB andUE operations according to embodiments of this disclosure;

FIG. 10 illustrates three examples of CSI-RS time-frequency patternswherein a pattern used for lower frequency resolution can be chosen as asubset of that for CSI-RS with higher frequency resolution according toembodiments of this disclosure;

FIG. 11 illustrates an example eNB and UE operations for semi-persistentCSI-RS according to embodiments of this disclosure;

FIG. 12 illustrates an example operating procedure for synchronizationaccording to embodiments of this disclosure;

FIG. 13 illustrates an example PSS transmission over a single symbol andover multiple symbols according to embodiments of this disclosure;

FIG. 14A illustrates an example of a single symbol PSS transmission frommultiple cells where the UE receives different PSS from neighboringcells according to embodiments of this disclosure;

FIG. 14B illustrates an example for multiple symbol transmission withthe PSS sequences being rotated for multiple cells according toembodiments of this disclosure;

FIG. 15 illustrates examples of PSS transmission design for single andmultiple symbol PSS configuration according to embodiments of thisdisclosure;

FIG. 16A-16C illustrate examples where the PSS is extended in thefrequency domain according to embodiments of this disclosure;

FIG. 16D illustrates an example where the UE scans for the PSSextensions in different RE groups according to embodiments of thisdisclosure;

FIG. 17 illustrates an example SSS transmission for single and multiplesymbol transmission according to embodiments of this disclosure;

FIG. 18 illustrates an example where a symbol offset information isincluded in a Master Information Block (MIB) transmitted via PBCHaccording to embodiments of this disclosure;

FIG. 19A illustrates an example frame structure that shows the placementof the PSS, SSS and PBCH for a single symbol transmission according toembodiments of this disclosure;

FIG. 19B illustrates an example frame structure that shows the placementof the PSS, SSS and PBCH for a multiple symbol transmission according toembodiments of this disclosure;

FIG. 19C illustrates an example frame structure where the PSS, SSS andPBCH are frequency division multiplexed according to embodiments of thisdisclosure;

FIG. 20A illustrates an example where PSS transmission is repeatedaccording to embodiments of this disclosure;

FIG. 20B illustrates another example where PSS transmission is repeatedaccording to embodiments of this disclosure;

FIG. 21 illustrates a flowchart for an example method wherein a UEreceives RS resource configuration information and at least two RS2according to an embodiment of the present disclosure; and

FIG. 22 illustrates a flowchart for an example method wherein a BSconfigures a UE (labeled as UE-k) with RS resources according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 22, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure can beimplemented in any suitably arranged wireless communication system.

List of Acronyms

-   -   2D: two-dimensional    -   MIMO: multiple-input multiple-output    -   SU-MIMO: single-user MIMO    -   MU-MIMO: multi-user MIMO    -   3GPP: 3rd generation partnership project    -   LTE: long-term evolution    -   UE: user equipment    -   eNB: evolved Node B or “eNB”    -   BS: base station    -   DL: downlink    -   UL: uplink    -   CRS: cell-specific reference signal(s)    -   DMRS: demodulation reference signal(s)    -   SRS: sounding reference signal(s)    -   UE-RS: UE-specific reference signal(s)    -   CSI-RS: channel state information reference signals    -   SCID: scrambling identity    -   MCS: modulation and coding scheme    -   RE: resource element    -   CQI: channel quality information    -   PMI: precoding matrix indicator    -   RI: rank indicator    -   MU-CQI: multi-user CQI    -   CSI: channel state information    -   CSI-IM: CSI interference measurement    -   CoMP: coordinated multi-point    -   DCI: downlink control information    -   UCI: uplink control information    -   PDSCH: physical downlink shared channel    -   PDCCH: physical downlink control channel    -   PUSCH: physical uplink shared channel    -   PUCCH: physical uplink control channel    -   PRB: physical resource block    -   RRC: radio resource control    -   AoA: angle of arrival    -   AoD: angle of departure

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP Technical Specification (TS) 36.211 version 12.4.0,“E-UTRA, Physical channels and modulation” (“REF 1”); 3GPP TS 36.212version 12.3.0, “E-UTRA, Multiplexing and Channel coding” (“REF 2”);3GPP TS 36.213 version 12.4.0, “E-UTRA, Physical Layer Procedures” (“REF3”); 3GPP TS 36.321 version 12.4.0, “E-UTRA, Medium Access Control (MAC)Protocol Specification” (“REF 4”); and 3GPP TS 36.331 version 12.4.0,“E-UTRA, Radio Resource Control (RRC) Protocol Specification” (“REF 5”).

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

FIG. 1 illustrates an example wireless network 100 according to variousembodiments of the present disclosure. The embodiment of the wirelessnetwork 100 shown in FIG. 1 is for illustration only. Other embodimentsof the wireless network 100 could be used without departing from thescope of the present disclosure.

The wireless network 100 includes an eNodeB (eNB) 101, an eNB 102, andan eNB 103. The eNB 101 communicates with the eNB 102 and the eNB 103.The eNB 101 also communicates with at least one Internet Protocol (IP)network 130, such as the Internet, a proprietary IP network, or otherdata network. Instead of “eNB”, an alternative term “gNB” (general NodeB) can also be used. Depending on the network type, other well-knownterms can be used instead of “eNB” or “BS,” such as “base station” or“access point.” For the sake of convenience, the terms “eNB” and “BS”are used in this patent document to refer to network infrastructurecomponents that provide wireless access to remote terminals. Also,depending on the network type, other well-known terms can be usedinstead of “user equipment” or “UE,” such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” or “userdevice.” For the sake of convenience, the terms “user equipment” and“UE” are used in this patent document to refer to remote wirelessequipment that wirelessly accesses an eNB, whether the UE is a mobiledevice (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which can belocated in a small business (SB); a UE 112, which can be located in anenterprise (E); a UE 113, which can be located in a WiFi hotspot (HS); aUE 114, which can be located in a first residence (R); a UE 115, whichcan be located in a second residence (R); and a UE 116, which can be amobile device (M) like a cell phone, a wireless laptop, a wireless PDA,or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 cancommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, or other advanced wireless communication techniques.

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, can have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of eNB 101, eNB 102, andeNB 103 transmit measurement reference signals to UEs 111-116 andconfigure UEs 111-116 for CSI reporting as described in embodiments ofthe present disclosure. In various embodiments, one or more of UEs111-116 receive and measure at least one transmission of measurementreference signals.

Although FIG. 1 illustrates one example of a wireless network 100,various changes can be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to the present disclosure. In the following description, atransmit path 200 can be described as being implemented in an eNB (suchas eNB 102), while a receive path 250 can be described as beingimplemented in a UE (such as UE 116). However, it will be understoodthat the receive path 250 could be implemented in an eNB and that thetransmit path 200 could be implemented in a UE. In some embodiments, thereceive path 250 is configured to receive and measure at least onemeasurement reference signal as described in embodiments of the presentdisclosure.

The transmit path 200 includes a channel coding and modulation block205, a serial-to-parallel (S-to-P) block 210, a size N Inverse FastFourier Transform (IFFT) block 215, a parallel-to-serial (P-to-S) block220, an add cyclic prefix block 225, and an up-converter (UC) 230. Thereceive path 250 includes a down-converter (DC) 255, a remove cyclicprefix block 260, a serial-to-parallel (S-to-P) block 265, a size N FastFourier Transform (FFT) block 270, a parallel-to-serial (P-to-S) block275, and a channel decoding and demodulation block 280.

In the transmit path 200, the channel coding and modulation block 205receives a set of information bits, applies coding (such asconvolutional, Turbo, or low-density parity check (LDPC) coding), andmodulates the input bits (such as with Quadrature Phase Shift Keying(QPSK) or Quadrature Amplitude Modulation (QAM)) to generate a sequenceof frequency-domain modulation symbols. The serial-to-parallel block 210converts (such as de-multiplexes) the serial modulated symbols toparallel data in order to generate N parallel symbol streams, where N isthe IFFT/FFT size used in the eNB 102 and the UE 116. The size N IFFTblock 215 performs an IFFT operation on the N parallel symbol streams togenerate time-domain output signals. The parallel-to-serial block 220converts (such as multiplexes) the parallel time-domain output symbolsfrom the size N IFFT block 215 in order to generate a serial time-domainsignal. The ‘add cyclic prefix’ block 225 inserts a cyclic prefix to thetime-domain signal. The up-converter 230 modulates (such as up-converts)the output of the ‘add cyclic prefix’ block 225 to an RF frequency fortransmission via a wireless channel. The signal can also be filtered atbaseband before conversion to the RF frequency.

A transmitted RF signal from the eNB 102 arrives at the UE 116 afterpassing through the wireless channel, and reverse operations to those atthe eNB 102 are performed at the UE 116. The down-converter 255down-converts the received signal to a baseband frequency, and theremove cyclic prefix block 260 removes the cyclic prefix to generate aserial time-domain baseband signal. The serial-to-parallel block 265converts the time-domain baseband signal to parallel time domainsignals. The size N FFT block 270 performs an FFT algorithm to generateN parallel frequency-domain signals. The parallel-to-serial block 275converts the parallel frequency-domain signals to a sequence ofmodulated data symbols. The channel decoding and demodulation block 280demodulates and decodes the modulated symbols to recover the originalinput data stream.

As described in more detail below, the transmit path 200 or the receivepath 250 can perform signaling for CSI reporting. Each of the eNBs101-103 can implement a transmit path 200 that is analogous totransmitting in the downlink to UEs 111-116 and can implement a receivepath 250 that is analogous to receiving in the uplink from UEs 111-116.Similarly, each of UEs 111-116 can implement a transmit path 200 fortransmitting in the uplink to eNBs 101-103 and can implement a receivepath 250 for receiving in the downlink from eNBs 101-103.

Each of the components in FIGS. 2A and 2B can be implemented using onlyhardware or using a combination of hardware and software/firmware. As aparticular example, at least some of the components in FIGS. 2A and 2Bcan be implemented in software, while other components can beimplemented by configurable hardware or a mixture of software andconfigurable hardware. For instance, the FFT block 270 and the IFFTblock 215 can be implemented as configurable software algorithms, wherethe value of size N can be modified according to the implementation.

Furthermore, although described as using FFT and IFFT, this is by way ofillustration only and should not be construed to limit the scope of thepresent disclosure. Other types of transforms, such as Discrete FourierTransform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions,could be used. It will be appreciated that the value of the variable Ncan be any integer number (such as 1, 2, 3, 4, or the like) for DFT andIDFT functions, while the value of the variable N can be any integernumber that is a power of two (such as 1, 2, 4, 8, 16, or the like) forFFT and IFFT functions.

Although FIGS. 2A and 2B illustrate examples of wireless transmit andreceive paths, various changes can be made to FIGS. 2A and 2B. Forexample, various components in FIGS. 2A and 2B could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs. Also, FIGS. 2A and 2B are meant toillustrate examples of the types of transmit and receive paths thatcould be used in a wireless network. Other suitable architectures couldbe used to support wireless communications in a wireless network.

FIG. 3A illustrates an example UE 116 according to the presentdisclosure. The embodiment of the UE 116 illustrated in FIG. 3A is forillustration only, and the UEs 111-115 of FIG. 1 could have the same orsimilar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3A does not limit the scope of the presentdisclosure to any particular implementation of a UE.

The UE 116 includes an antenna 305, a radio frequency (RF) transceiver310, transmit (TX) processing circuitry 315, a microphone 320, andreceive (RX) processing circuitry 325. The UE 116 also includes aspeaker 330, a processor 340, an input/output (I/O) interface (IF) 345,an input 350, a display 355, and a memory 360. The memory 360 includesan operating system (OS) program 361 and one or more applications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS program 361 stored in the memory 360 in orderto control the overall operation of the UE 116. For example, processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as operations for CQImeasurement and reporting for systems described in embodiments of thepresent disclosure as described in embodiments of the presentdisclosure. The processor 340 can move data into or out of the memory360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS program 361 or in response to signals received from eNBs or anoperator. The processor 340 is also coupled to the I/O interface 345,which provides the UE 116 with the ability to connect to other devicessuch as laptop computers and handheld computers. The I/O interface 345is the communication path between these accessories and the processor340.

The processor 340 is also coupled to the input 350 (e.g., keypad,touchscreen, button etc.) and the display 355. The operator of the UE116 can use the input 350 to enter data into the UE 116. The display 355can be a liquid crystal display or other display capable of renderingtext and/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

As described in more detail below, the UE 116 can perform signaling andcalculation for CSI measurement and reporting. Although FIG. 3Aillustrates one example of UE 116, various changes can be made to FIG.3A. For example, various components in FIG. 3A could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs. As a particular example, the processor340 could be divided into multiple processors, such as one or morecentral processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3A illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 3B illustrates an example eNB 102 according to the presentdisclosure. The embodiment of the eNB 102 shown in FIG. 3B is forillustration only, and other eNBs of FIG. 1 could have the same orsimilar configuration. However, eNBs come in a wide variety ofconfigurations, and FIG. 3B does not limit the scope of the presentdisclosure to any particular implementation of an eNB. eNB 101 and eNB103 can include the same or similar structure as eNB 102.

As shown in FIG. 3B, the eNB 102 includes multiple antennas 370 a-370 n,multiple RF transceivers 372 a-372 n, transmit (TX) processing circuitry374, and receive (RX) processing circuitry 376. In certain embodiments,one or more of the multiple antennas 370 a-370 n include 2D antennaarrays. The eNB 102 also includes a controller/processor 378, a memory380, and a backhaul or network interface 382.

The RF transceivers 372 a-372 n receive, from the antennas 370 a-370 n,incoming RF signals, such as signals transmitted by UEs or other eNBs.The RF transceivers 372 a-372 n down-convert the incoming RF signals togenerate IF or baseband signals. The IF or baseband signals are sent tothe RX processing circuitry 376, which generates processed basebandsignals by filtering, decoding, and/or digitizing the baseband or IFsignals. The RX processing circuitry 376 transmits the processedbaseband signals to the controller/processor 378 for further processing.

The TX processing circuitry 374 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 378. The TX processing circuitry 374 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 372 a-372 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 374 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 370 a-370 n.

The controller/processor 378 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 378 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 372 a-372 n, the RX processing circuitry 376, andthe TX processing circuitry 374 in accordance with well-knownprinciples. The controller/processor 378 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. In some embodiments, the controller/processor 378 includes atleast one microprocessor or microcontroller.

The controller/processor 378 is also capable of executing programs andother processes resident in the memory 380, such as an OS. Thecontroller/processor 378 is also capable of supporting channel qualitymeasurement and reporting for systems having 2D antenna arrays asdescribed in embodiments of the present disclosure. In some embodiments,the controller/processor 378 supports communications between entities,such as web RTC. The controller/processor 378 can move data into or outof the memory 380 as required by an executing process.

The controller/processor 378 is also coupled to the backhaul or networkinterface 382. The backhaul or network interface 382 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 382 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G or new radio access technology or NR, LTE, or LTE-A),the interface 382 could allow the eNB 102 to communicate with other eNBsover a wired or wireless backhaul connection. When the eNB 102 isimplemented as an access point, the interface 382 could allow the eNB102 to communicate over a wired or wireless local area network or over awired or wireless connection to a larger network (such as the Internet).The interface 382 includes any suitable structure supportingcommunications over a wired or wireless connection, such as an Ethernetor RF transceiver.

The memory 380 is coupled to the controller/processor 378. Part of thememory 380 could include a RAM, and another part of the memory 380 couldinclude a Flash memory or other ROM. In certain embodiments, a pluralityof instructions, such as a BIS algorithm is stored in memory. Theplurality of instructions are configured to cause thecontroller/processor 378 to perform the BIS process and to decode areceived signal after subtracting out at least one interfering signaldetermined by the BIS algorithm.

As described in more detail below, the transmit and receive paths of theeNB 102 (implemented using the RF transceivers 372 a-372 n, TXprocessing circuitry 374, and/or RX processing circuitry 376) performconfiguration and signaling for CSI reporting.

Although FIG. 3B illustrates one example of an eNB 102, various changescan be made to FIG. 3B. For example, the eNB 102 could include anynumber of each component shown in FIG. 3A. As a particular example, anaccess point could include a number of interfaces 382, and thecontroller/processor 378 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry374 and a single instance of RX processing circuitry 376, the eNB 102could include multiple instances of each (such as one per RFtransceiver).

Rel.13 LTE supports up to 16 CSI-RS antenna ports which enable an eNB tobe equipped with a large number of antenna elements (such as 64 or 128).In this case, a plurality of antenna elements is mapped onto one CSI-RSport. Furthermore, up to 32 CSI-RS ports will be supported in Rel.14LTE. For next generation cellular systems such as 5G, it is expectedthat the maximum number of CSI-RS ports remain more or less the same.

For mmWave bands, although the number of antenna elements can be largerfor a given form factor, the number of CSI-RS ports—which can correspondto the number of digitally precoded ports—tends to be limited due tohardware constraints (such as the feasibility to install a large numberof ADCs/DACs at mmWave frequencies) as illustrated in transmitter 400illustrated of FIG. 4. In this case, one CSI-RS port is mapped onto alarge number of antenna elements which can be controlled by a bank ofanalog phase shifters 401. One CSI-RS port can then correspond to onesub-array which produces a narrow analog beam through analog beamforming405. This analog beam can be configured to sweep across a wider range ofangles (420) by varying the phase shifter bank across symbols orsubframes. The number of sub-arrays (equal to the number of RF chains)is the same as the number of CSI-RS ports N_(CSI-PORT). A digitalbeamforming unit 410 performs a linear combination across N_(CSI-PORT)analog beams to further increase precoding gain. While analog beams arewideband (hence not frequency-selective), digital precoding can bevaried across frequency sub-bands or resource blocks.

To enable digital precoding, efficient design of CSI-RS is a crucialfactor. For this reason, three types of CSI reporting mechanismcorresponding to three types of CSI-RS measurement behavior aresupported in Rel.13 LTE: 1) ‘CLASS A’ CSI reporting which corresponds tonon-precoded CSI-RS, 2) ‘CLASS B’ reporting with K=1 CSI-RS resourcewhich corresponds to UE-specific beamformed CSI-RS, 3) ‘CLASS B’reporting with K>1 CSI-RS resources which corresponds to cell-specificbeamformed CSI-RS. For non-precoded (NP) CSI-RS, a cell-specificone-to-one mapping between CSI-RS port and TXRU is utilized. Here,different CSI-RS ports have the same wide beam width and direction andhence generally cell wide coverage. For beamformed CSI-RS, beamformingoperation, either cell-specific or UE-specific, is applied on anon-zero-power (NZP) CSI-RS resource (consisting of multiple ports).Here, (at least at a given time/frequency) CSI-RS ports have narrow beamwidths and hence not cell wide coverage, and (at least from the eNBperspective) at least some CSI-RS port-resource combinations havedifferent beam directions.

In scenarios where DL long-term channel statistics can be measuredthrough UL signals at a serving eNB, UE-specific BF CSI-RS can bereadily used. This is typically feasible when UL-DL duplex distance issufficiently small. When this condition does not hold, however, some UEfeedback is necessary for the eNB to obtain an estimate of DL long-termchannel statistics (or any of its representation thereof). To facilitatesuch a procedure, a first BF CSI-RS transmitted with periodicity T1 (ms)and a second NP CSI-RS transmitted with periodicity T2 (ms), whereT1≤T2. This approach is termed hybrid CSI-RS. The implementation ofhybrid CSI-RS is largely dependent on the definition of CSI process andNZP CSI-RS resource.

As discussed above, utilizing UE-specific BF CSI-RS reduces the numberof ports configured to each UE by applying beamforming on NP CSI-RS. Forinstance, a serving eNB can apply wideband beamforming on a 16-port NPCSI-RS to form a 2-port BF CSI-RS for a served UE. If each UE isconfigured with 2-port BF CSI-RS, the resulting total CSI-RS overhead isreduced when the number of co-scheduled UEs is less than 8—assuming thesame transmission rate for NP and BF CSI-RS. However, although not allthe served UEs require data transmission in every subframe, the numberof served UEs per cell tends to be much larger than 8. Due to theburstiness and stochasticity of data traffic, UE-specific BF CSI-RSrequires an efficient CSI-RS resource allocation mechanism to ensurethat the total CSI-RS overhead can be minimized or, conversely, thenumber of served UEs per cell can be maximized.

For next generation cellular systems (especially enhanced mobilebroadband, or often termed eMBB, scenarios), efficient CSI-RS resourceallocation mechanism and CSI measurements become more critical as thenumber of UEs serviced per cell will increase along with theirthroughput requirements. While the three-type CSI-RS design in Rel.13LTE can cater for different scenarios, redundancies exist especiallybetween NP CSI-RS (with partial port mapping) and cell-specific BFCSI-RS. Furthermore, CSI-RS resource utilization is based on periodictransmission and measurement. That is, CSI-RS is transmitted andmeasured periodically even when it is not needed. This results in someunnecessary throughput loss and increase in interference (inter andintra-cell). In addition, backward compatibility constraints (such asthe presence or non-presence of CRS) tend to restrict the potential ofCSI-RS.

Therefore, there is a need for a CSI-RS design which enables efficientresource allocation mechanism for next generation cellular systems andis free of the aforementioned constraints.

The present disclosure includes at least three components for CSI-RSdesign. A first component is a multi-level hierarchical CSI-RS design(with a special case of two-level CSI-RS): coverage CSI-RS andUE-specific CSI-RS, or multi-level CSI-RS. A second component istransmission procedure of the two types of CSI-RS. A third component isCSI measurement procedure associated with the design along with its DLand UL signaling supports.

For the first component (that is, multi-level hierarchical CSI-RS), oneembodiment can be described as follows. In one embodiment, two types orlevels of CSI-RS are utilized: coverage CSI-RS (type 1) and UE-specificCSI-RS (type 2). In terms of design, they can be differentiated based ontheir coverage areas, the number of ports, resource pools, resolutions,or the physical channels the CSI-RS types are associated with. The names‘coverage CSI-RS’ and ‘UE-specific CSI-RS’ are exemplary and can besubstituted with other names or labels without changing the substance ofthis embodiment.

A coverage CSI-RS can be transmitted to provide coverage for a widerarea within a cell. This wide area can constitute a virtual sector whereall the K virtual sectors share the same cell identification (cell ID).Each virtual sector k corresponds to one coverage CSI-RS hence oneCSI-RS resource of N_(k) CSI-RS ports. At least one of the K CSI-RSresources can be precoded (beamformed) to ensure that the coverageCSI-RS can attain the desired coverage. Therefore, a coverage CSI-RS istransmitted by an eNB along a directional beam whose width and depth(penetration/reach) reach a targeted group of UEs. A special case of K=1corresponds to one virtual sector per cell. In this case, one commoncoverage CSI-RS is used for one entire cell. Since there is nosectorization, coverage CSI-RS can be transmitted with anomnidirectional beam pattern.

Associating a coverage CSI-RS with a virtual sector can be relevantespecially for sub-6-GHz frequency bands. Another possibility(especially applicable for mmWave frequency bands) is to associate acoverage CSI-RS with coarse spatial granularity. In this sub-embodiment,a set of K coverage CSI-RS resources—and their correspondingbeams—facilitates coarse spatial synchronization which is analogous tocoarse timing and frequency synchronization via synchronization signals(primary synchronization signal PSS and/or secondary synchronizationsignal SSS).

An exemplary embodiment implements this scheme by allowing simultaneoustransmission of K coverage beams (associated with K coverage CSI-RSresources) either in time-domain or frequency domain or bothtime-frequency domain. This sub-embodiment can be used in eithersub-6-GHz or mmWave bands although it is more relevant in sub-6-GHzwhere transmitting multiple beams simultaneously results in lowpenetration (as the total eNB transmit power can be distributed across Kbeams while still meeting the link budget).

Another exemplary sub-embodiment implements this scheme by sweepingacross K coverage beams (associated with K coverage CSI-RS resources) intime-domain. That is, at a given time unit (such as symbol or subframen), a coverage CSI-RS (associated with one CSI-RS resource) istransmitted on one of the K beams (such as beam mod(n,K)). This isillustrated in FIG. 7 where each sub-array generates an analog beamwhich forms a sweeping coverage beam across time units. In this example,K=6. The directions of these beams, associated with K beamformingvectors, are either static or semi-static. This sub-embodiment can beused in either sub-6-GHz or mmWave bands although it is more relevant inmmWave where transmitting multiple beams simultaneously results in lowpenetration (as the total eNB transmit power is distributed across Kbeams and hence K coverage CSI-RSs and propagation loss is higher).

Another exemplary sub-embodiment implements this scheme by allowingsimultaneous transmission of K coverage beams (associated with Kcoverage CSI-RS resources) in time-domain but multiplexing K coveragebeams (associated with K coverage CSI-RS resources) in frequency-domain.That is, in a given frequency unit (such as PRB or a collection ofPRBs), coverage CSI-RS is transmitted on one of the K beams (such asbeam mod(n,K)). This is illustrated in FIG. 4 where each sub-arraygenerates an analog beam which forms a sweeping coverage beam acrossfrequency units. In this example, K=6. The directions of these beams,associated with K beamforming vectors, are either static or semi-static.This sub-embodiment can be used in either sub-6-GHz or mmWave bandswhere frequency-selective (subband) beamforming is feasible.

A UE-specific CSI-RS can be transmitted to facilitate more accurate andfocused DL channel measurement. While a coverage CSI-RS facilitates DLchannel measurement over a wider area or range of directions and isintended to be measured by a group of UEs, UE-specific CSI-RSfacilitates DL channel measurement over a narrower area or range ofdirections and is intended to be measured by a particular UE (or at mosta small number of co-located UEs).

At least two sub-embodiments of UE-specific CSI-RS can be devised. Afirst sub-embodiment utilizes UE-specific beamforming derived from anacquired CSI at the eNB on CSI-RS ports. The beamforming operation isderived independently from coverage CSI-RS. A second sub-embodimentutilizes UE-specific beamforming which is calculated relative to thebeamforming applied on coverage CSI-RS. Therefore, the resultantbeamforming operation applied on UE-specific CSI-RS includes thebeamforming applied on coverage CSI-RS (as a first stage) as well as theadditional UE-specific beamforming (as a second stage). The resultantUE-specific beam corresponds to a subspace of the coverage beam.

Just as coverage CSI-RS, UE-specific CSI-RS can include L>1 UE-specificbeams (associated with L UE-specific CSI-RS resources). Each of these LUE-specific CSI-RS resources can comprise one or multiple antenna portsand be utilized to form a higher-resolution beam. For instance, a UEconfigured with an L-resource/beam UE-specific CSI-RS can measure Lhigher-resolution CSI-RS beams and select a subset of L beams, alongwith their CSIs or RSRPs, for the purpose of CSI acquisition.

FIG. 5 illustrates the above two-level CSI-RS design 500 according toembodiments of this disclosure. An eNB 501 transmits two coverageCSI-RSs 510 and 550 on two coverage beams to two UEs 502 and 503. Thesetwo coverage beams 0 and 1 (hence two coverage CSI-RSs) can betransmitted simultaneously or multiplexed in time or frequency. Usingthe second sub-embodiment of UE-specific CSI-RS, the eNB transmits twoUE-specific CSI-RSs 0.0 (520) and 0.1 (530). The two UE-specific beamsutilized for transmitting the two UE-specific CSI-RSs are derivedrelative to the first coverage beam and hence correspond to subspaces ofthe coverage beam. Since these two UE-specific beams are transmittedalong a smaller range of directions, they have higher penetration due toadditional beamforming gains. The second UE 503 measures UE-specificCSI-RS 530 and receives data transmission from the eNB along a data beam0.1.0 (535). Beamforming vector for the data beam can be formed eitherfrom a CSI reporting derived from the UE-specific CSI-RS 530 (relevantfor FDD) or measuring UL SRS (relevant for TDD).

FIG. 6 illustrates an exemplary use case of the two-level CSI-RS designin a cellular deployment 600 according to embodiments of thisdisclosure. Only one cell 610 is shown in this description. Eightcoverage CSI-RSs along with their beams (620) and two UE-specificCSI-RSs associated with two different coverage CSI-RSs (630) areutilized. One data transmission along a beam 640 is shown. Compared toUE-specific CSI-RS, coverage CSI-RS is measured by a larger number ofUEs. For instance, UE-specific CSI-RS can be configured for (and hencemeasured by) only one UE. Coverage CSI-RS, on the other hand, can beconfigured for (and hence measured by) all the UEs within one sector orsub-cell.

While FIG. 6 employs two-level CSI-RS design, FIG. 7 illustrates anexemplary embodiment with a three-level CSI-RS design in a cellulardeployment 700 according to embodiments of this disclosure. Only onecell 710 is shown in this description. A first-level CSI-RS 720 istransmitted along an omni-directional beam (hence wide coverage) yetweaker penetration (reach). There is only one level-one CSI-RS. Athird-level CSI-RS 740 is transmitted along a beam with narrow coverageyet stronger penetration (reach). A level-two CSI-RS 730 uses a beamwith wider coverage than level-three and weaker penetration (reach) thanlevel-two. There are eight level-two CSI-RSs shown in FIG. 7. One datatransmission along a beam 750 is shown. In general, compared to level-nCSI-RS, level-(n−1) CSI-RS is measured by a larger number of UEs (n=2,3, . . . , K).

Any of the M CSI-RS types/levels (type/level m) can include L_(m)≥1beams (associated with L UE-specific CSI-RS resources). Each of these LCSI-RS resources can comprise one or multiple antenna ports. Forinstance, a UE configured with an L_(m)-resource/beam CSI-RS can measureL_(m) higher-resolution CSI-RS beams and select a subset of L_(m) beams,along with their CSIs or RSRPs, for the purpose of CSI acquisition.

In one embodiment for resource allocation, the aforementioned levels ortypes of CSI-RS can be derived from a common pool of CSI-RS resources.In another embodiment, each type of CSI-RS can be derived from adistinct pool of CSI-RS resources. The first embodiment allows moreefficient resource utilization.

When an eNB configures a UE with a plurality of CSI-RS types, the eNBcan differentiate between these CSI-RS types in several manners. A firstpossibility is to configure a UE with M CSI-RS resources and each of theM CSI-RS resources is associated (or carries) a configuration parameterindicating the CSI-RS type or level. This CSI-RS type will dictate UECSI measurement behavior. A second possibility is to configure a UE withM CSI-RS resources without any parameter indicating the CSI-RS type orlevel. The coverage and penetration of each of the M CSI-RS resourcesare transparent to the UE. Either way, this CSI-RS configurationinformation (for each of the M CSI-RS resources) can be signaled to theUE either semi-statically via higher-layer (RRC) signaling ordynamically via MAC control element (MAC CE) or L1 control channel(s).Moreover, these M CSI-RS resources can be associated with one CSIprocess or K CSI processes (where one CSI-RS resource corresponds to oneCSI process).

Similar to coverage CSI-RS, an exemplary embodiment implements thisscheme by allowing simultaneous transmission of M CSI-RS resources(associated with M beams) either in time-domain (time subsampling), orfrequency domain (frequency subsampling), or neither time nor frequency(time-frequency subsampling), or both time-frequency domain. The firstthree options allow an eNB to map (hence a UE to measure) only a subsetof CSI-RS ports for a given time and/or frequency unit (such assubframe/slot and frequency resource block). This can be termedpartial-port mapping. The last option allows an eNB to map (hence a UEto measure) all the CSI-RS ports for a given time and/or frequency unit(such as subframe/slot and frequency resource block). This can be termedfull-port mapping.

For the second component (that is, CSI-RS transmission procedure andconfiguration), one embodiment can be described as follows. In oneconfiguration embodiment, all the CSI-RS levels can be configured viahigher-layer (RRC) signaling, MAC control element (MAC CE), and/or DL L1control signaling (based on DCI). In this case, such configuration isUE-specific.

To configure a UE with M CSI-RS resources, CSI-RS resource configurationwhich carries a set of UE-specific parameters can be used. Thisconfiguration can be transmitted to the UE via either higher-layer (RRC)signaling, MAC control element (MAC CE), and/or DL L1 control signaling(based on DCI).

When a UE is configured with M CSI-RS resources, at least three schemesexist. These three possibilities are illustrated in FIG. 8. A firstscheme 800 is to use a common resource configuration which applies toall the M resources (801 in scheme 800 of FIG. 8). Such a commonconfiguration includes all applicable CSI-RS resource parameters. Thisallows an eNB to configure a UE with M identical CSI-RS resources (806,807, and 808 in scheme 800 of FIG. 8). Although this commonconfiguration can be signaled via higher-layer (RRC) signaling, MACcontrol element (MAC CE), and/or DL L1 control signaling (based on DCI),signaling via higher-layer (RRC) signaling seems to be a first choice.This scheme, however, can be too restrictive for multi-level CSI-RS.

A second scheme 810 is to use M independent/separate resourceconfigurations (812, 813, and 814 in scheme 810 of FIG. 8). Each of theM CSI-RS resource-specific configurations includes all applicable CSI-RSresource parameters. This allows full flexibility for multi-level CSI-RSsince each of the M resources can be configured independently (816, 817,and 818 in scheme 810 of FIG. 8). Each of the M separate configurationscan be signaled via higher-layer (RRC) signaling, MAC control element(MAC CE), and/or DL L1 control signaling (based on DCI).

A third scheme 820 is to use one CSI-RS resource configuration whichcontains only a set of parameters common to all the M CSI-RS resources(821 in scheme 820 of FIG. 8) and M sub-configurations (822, 823, and824 in scheme 820 of FIG. 8), each of which containing a different setof parameters specific to each of the M CSI-RS resources (826, 827, and828 in scheme 820 of FIG. 8). The first and second sets of parametersare termed set A and B, respectively, where A∪B contains all CSI-RSresource configuration parameters while A∩B=Ø (no overlapping) oroverlapping. In principle, scheme 2 is suitable when M CSI-RS resourcescorrespond to M CSI-RS with different resolutions in space, time, and/orfrequency dimensions. On the other hand, scheme 3 is suitable when MCSI-RS resources correspond to M CSI-RS with a same resolution (inspace, time, and/or frequency dimensions) but are pointed at differentbeam directions. An example configuration signaling for this thirdscheme is to signal the common configuration via higher-layer (RRC)signaling, and each of the M separate configurations via eitherhigher-layer (RRC) signaling, MAC control element (MAC CE), and/or DL L1control signaling (based on DCI). That is, the signaling of a separateconfiguration can be semi-static (via RRC signaling) or dynamic (via MACCE or L1 DL control signaling).

In another configuration embodiment, all the CSI-RS levels can beconfigured via common control signaling (such as broadcast channels),higher-layer (RRC) signaling, MAC control element (MAC CE), and/or DL L1control signaling (based on DCI). In this case, such configuration isUE-specific. The use of common control signaling is suitable for level Iand/or coverage CSI-RS which are cell-/TRP(transmit-receive-point)-/gNB-/eNB-/UE-group-specific (or, in general,non-UE-specific) rather than UE-specific. Common control signaling cancomprise including the pertinent configuration information in the MasterInformation Block (MIB) which is received by a UE via Primary BroadcastChannel (P-BCH). Alternatively, it can comprise including the pertinentconfiguration information in one of the System Information Blocks(SIB-x) which is received by a UE via an L1 DL control channel (such asPDCCH).

In this case, all the three embodiments in FIG. 8 (800, 810, or 820)apply. However, the common configuration information (component 801 or821) is signaled via common control signaling—either included in MIB(received via P-BCH) or SIB-x (received via an L1 DL control channel).Each of the M separate configurations via either higher-layer (RRC)signaling, MAC control element (MAC CE), and/or DL L1 control signaling(based on DCI).

In the present disclosure, the aforementioned CSI-RS resourceconfiguration contains at least one of the following categories ofparameters: 1) CSI-RS type or level (as previously mentioned), 2)Time-domain configuration, 3) Frequency-domain configuration, 4) CSI-RSport subset configuration.

As previously mentioned, CSI-RS type or level corresponds to a level ofpenetration and coverage of a CSI-RS resource. This level can be eitherabsolute or relative. An absolute level can be a value which representsa power measure such as EPRE (energy-per-resource element) either in dB(relative to a fixed reference) or dBm. This can be defined relative todata transmission power or relative to a cell-specific RS. For thesecond option, level-one (for instance, coverage) CSI-RS, if configuredas a cell-specific RS, can be used as a reference for both data andlevel-n CSI-RS where n>1 (for instance, UE-specific CSI-RS). A relativelevel can reflect difference in coverage and/or penetration across the Mconfigured CSI-RS resources. For example, analogous to FIG. 7, M=4 withthe first, second, third, and fourth CSI-RS level as 1, 2, 2, and 3,respectively, indicates that the second and third CSI-RS resources areof a same level of coverage and penetration, but of a higher penetration(hence lower coverage) than the first CSI-RS resource, and of a lowerpenetration (hence higher coverage) than the fourth CSI-RS resource.

The content of time-domain configuration can include periodicity andtime unit (for instance, one slot or one subframe) offset when periodicCSI-RS transmission from an eNB and/or periodic CSI-RS measurement at aUE are assumed. However, if a UE shall assume that either CSI-RS istransmitted aperiodically or CSI-RS is measured aperiodically,periodicity and time unit offset are not needed. Instead, time-domainconfiguration includes a trigger or a flag signaled via a DL L1 controlchannel.

An embodiment of aperiodic CSI-RS, which includes eNB and UE operations,is illustrated in flow diagram 900 of FIG. 9. Aperiodic CSI-RS(Ap-CSI-RS) is characterized by two primary features. First, a pool ofCSI-RS resources is defined and shared among multiple served UEs (910).A CSI-RS resource from this pool is assigned to a UE only when the UEmeasures CSI through CSI-RS (hence a resource is used only when it isneeded). The UE needs to measure CSI when its associated serving eNBchooses to receive a CSI reporting calculated based on a most recentchannel.

This leads to a second primary feature. Ap-CSI-RS assignment is done inconjunction with an aperiodic CSI request from the serving eNB to aserved UE (in this example, termed UE-k). Therefore, Ap-CSI-RS resourceinformation is included in a DCI of an UL grant which contains anaperiodic CSI (A-CSI) request to UE-k in subframe n (920). Along with itis the Ap-CSI-RS itself, which is placed in the same DL subframe n asthe A-CSI trigger and the Ap-CSI-RS resource information. In anotherexample, the Ap-CSI-RS can be placed in another subframe followingsubframe n (at the expense of CSI reporting delay). In response to theCSI request and the Ap-CSI-RS resource information in subframe n(assuming that the Ap-CSI-RS is placed in subframe n), UE-k measures theassociated Ap-CSI-RS assigned by the eNB (930) and reports a requestedA-CSI in subframe n+L (940) where L is specified and can bescenario-dependent. For instance, a default value of L is 4 followingRel.13 LTE.

The content of frequency-domain configuration can include time-frequencyCSI-RS pattern within one time unit (for instance, one slot or onesubframe). Time-frequency pattern within one time unit describes thelocations of CSI-RS REs across sub-carriers and OFDM symbols. This holdsfor both periodic and aperiodic CSI-RS transmission from an eNB and/orCSI-RS measurement at a UE. Other than time-frequency pattern, a UE canalso be configured with a CSI-RS resource which spans only over aportion of the system bandwidth. For instance, a CSI-RS resource towhich the UE is assigned corresponds to only a set of m<M PRBs out ofthe entire system bandwidth which spans over M PRBs. This can be termedthe CSI-RS bandwidth, which can be configured either via higher layersignaling, UL grant or DL assignment via PDCCH/EPDCCH, or MAC controlelement via DL-SCH.

The content of port-subset configuration can include a subset of theavailable antenna ports and the number of antenna ports N_(PORT)configured for a UE. To define a set of CSI-RS port numbers assigned toa UE, a master set of all the available port numbers {Port₀, Port₀+1, .. . , Port₀+N_(PORT,MAX)−1} is needed. At least two options areavailable. For a given number of CSI-RS ports N_(PORT), an N_(PORT)-portCSI-RS resource can be specified in terms of a port-subset of the masterset {Port₀, Port₀+1, . . . , Port₀+N_(PORT,MAX)−1}. At least two optionsare possible.

In a first option for port subset selection, an N_(PORT)-port CSI-RSresource is always associated with port numbers {Port₀, Port₀+1, . . . ,Port₀+N_(PORT)−1}. That is, the assigned CSI-RS port numbers areconsecutive for any CSI-RS resource assignment. In this case, the set ofCSI-RS port numbers is fixed for a given number of CSI-RS ports. Giventhe number of CSI-RS ports N_(PORT), there is no need to indicate orsignal port subset selection in Ap-CSI-RS resource configuration.

A second option for port subset selection which offers more flexibleresource allocation and increased number of resource configurations isto allow a CSI-RS resource configuration to be associated with portnumbers {Port(0), Port(1), . . . , Port(N_(PORT)−1)} where Port(i) canbe any port number taken from the master set. A constraint ofPort(i)<Port(k), i>k can be further imposed. For a given value ofN_(PORT,MAX) and N_(PORT), a total of

$N_{cand} = \begin{pmatrix}N_{{PORT},{MAX}} \\N_{PORT}\end{pmatrix}$

candidates for CSI-RS port subset selection are available. Thus, if portsubset selection is unrestricted, all these candidates are available. Inanother example, only a part of these available candidates can be used.In that case, a restricted subset of available candidates

$N_{cand} < \begin{pmatrix}N_{{PORT},{MAX}} \\N_{PORT}\end{pmatrix}$

is used. For this second port subset selection option, port subsetselection is to be signaled and indicated in Ap-CSI-RS resourceconfiguration info. For this purpose, either a length-N_(PORT,MAX)bitmap (indicating which port numbers are assigned to a UE) or a ┌log₂N_(cand)┐-bit port subset indicator can be used. The bitmap isapplicable for either unrestricted or restricted subset selection. Thesubset indicator, on the other hand, is suitable for restricted subsetselection.

The four categories of CSI-RS resource configuration parameters arerelated to CSI-RS resolution in time, frequency, and antenna port(spatial beam). Therefore, CSI-RS subsampling can be performed in atleast one of these three dimensions. An exemplary embodiment is toassociate higher frequency resolution with aperiodic CSI-RS transmissionand measurement (only transmitted and/or measured when needed), butlower frequency resolution with periodic CSI-RS transmission andmeasurement. Lower frequency resolution can be attained with lowerCSI-RS RE density (frequency subsampling) which can be used inconjunction with beam-level subsampling.

To ensure that CSI reports associated with CSI-RS resources of differentfrequency resolutions can be jointly used at an eNB, the CSI-RStime-frequency (T-F) pattern used for lower frequency resolution can bechosen as a subset of that for CSI-RS with higher frequency resolution.This can be illustrated in FIG. 10 with three CSI-RS patterns 1000,1010, and 1020. In this example, 1000 uses 2 REs per PRB (hence ofhighest frequency resolution), while 1010 and 1020 use 1 RE per PRB and0.5 RE per PRB, respectively. When 0.5 RE/PRB is used, only the PRB 1021contains CSI-RS REs (frequency subsampling)—or a UE shall measure onlyPRB 1021 (every other PRBs) for computing CSI reports.

Therefore, in one embodiment, each of the M levels or types of CSI-RS isassociated with a set of CSI-RS T-F patterns (as exemplified above)wherein each of the M CSI-RS T-F patterns is associated with a frequencyresolution. A UE configured with an M-level/M-type CSI-RS can beconfigured with one of the CSI-RS T-F patterns for each level/type.

In a variation of the above embodiment, when M=2, the set of CSI-RS T-Fpatterns associated with the first level/type is a subset of thatassociated with the second level/type. In particular, if the firstlevel/type is coverage or non-UE-specific CSI-RS which iscell-/TRP-/gNB-/eNB-/UE-group-specific (or, in general,non-UE-specific), and the second level/type is UE-specific CSI-RS, theset of CSI-RS T-F patterns associated with coverage/non-UE-specificCSI-RS is a subset of a larger set of CSI-RS T-F patterns associatedwith UE-specific CSI-RS. In one example, maximum frequency densityassociated with coverage/non-UE-specific CSI-RS is lower than thatassociated with UE-specific CSI-RS.

In another variation of the above embodiment, when M=2, the maximumnumber of ports associated with first level/type is higher than thatassociated with the second level/type. In particular, if the firstlevel/type is coverage or non-UE-specific CSI-RS which iscell-/TRP-/gNB-/eNB-/UE-group-specific (or, in general,non-UE-specific), and the second level/type is UE-specific CSI-RS, themaximum number of ports associated with coverage/non-UE-specific CSI-RSis higher than that associated with UE-specific CSI-RS.

For the third component (that is, CSI measurement and reportingprocedure), one embodiment can be described as follows. Each CSI-RSresource can be associated with a set of CSI reports. If an eNBconfigures a UE with M CSI-RS resources, M sets of CSI-RS reports areexpected when the M CSI-RS resources are associated with differentresolutions. On the other hand, fewer than M sets of CSI reports (oreven one set) are suitable when M CSI-RS resources correspond to MCSI-RS with a same resolution (in space, time, and frequency) but arepointed at different beam directions. For the second case, a UE can alsoreport CSI-RS resource selection.

Likewise, low frequency resolution CSI-RS transmission (or low frequencyresolution CSI-RS measurement) can be associated with low-resolution CSIreporting. An exemplary embodiment of low-resolution CSI reporting iswideband CSI reporting where one CQI and PMI are reported for all theconfigured subbands. High frequency resolution CSI-RS transmission (orhigh frequency resolution CSI-RS measurement) can be associated withhigh-resolution CSI reporting. An exemplary embodiment ofhigh-resolution CSI reporting is to report one CQI per subband and/orsubband precoding recommendation. Instead of precoding recommendation,quantized channel coefficients can be reported.

In another embodiment, low frequency resolution CSI-RS transmission (orlow frequency resolution CSI-RS measurement) can be associated withhigh-resolution CSI reporting. An exemplary embodiment ofhigh-resolution CSI reporting is to report one CQI per subband and/orsubband precoding recommendation. (for instance, subband selection willbe done based on NP CSI-RS) High frequency resolution CSI-RStransmission (or high frequency resolution CSI-RS measurement) isassociated with low-resolution CSI reporting. An exemplary embodiment oflow-resolution CSI reporting is to report one CQI per subband and/orsubband co-phasing recommendation. Here, the high frequency resolutionCSI-RS can be transmitted in the given subband, for instance, similar tothe operation of demodulation-RS.

In addition, periodic CSI-RS is associated with periodic CSI (P-CSI)reporting while aperiodic CSI-RS (Ap-CSI-RS) is associated withaperiodic CSI (A-CSI) reporting.

Periodic CSI-RS and P-CSI reporting can be configured for a UE asfollows. First, an eNB configures a UE with at least one periodic CSI-RSresource and at least one P-CSI reporting (which at least includesreporting mode, periodicity, and subframe offset). These configurationscan be signaled to the UE via higher-layer signaling. Based on thesubframe offsets and periodicity of CSI-RS and P-CSI reporting, the UEmeasures CSI-RS and reports P-CSI periodically with a predeterminedtiming relationship between CSI-RS and CSI reporting.

For Ap-CSI-RS and A-CSI reporting, at least three options are possiblefor signaling each of the three parameters associated with CSI-RSresource configuration (such as number of antenna ports, T-F patternconfiguration, and port subset configuration).

A first option is to use RRC signaling per UE to perform semi-static(re)configuration of CSI-RS resource. Several served UEs can beconfigured to share a same CSI-RS resource assignment or haveoverlapping resource assignments.

A second option is to use UL grant by incorporating the parameter in anassociated DCI which carries A-CSI request (trigger). Therefore, CSI-RSresource configuration is signaled dynamically.

A third option is to use periodic resource (re)configuration using asimilar principle to semi-persistent scheduling (SPS). That is, an ULgrant is used to signal a reconfigured CSI-RS resource assignment to aserved UE-k. This CSI-RS resource assignment can be accompanied withA-CSI request (trigger) or signaled by itself. This periodic CSI-RSresource (re)configuration is performed every X ms where X can beconfigured via RRC signaling. The value of X can be chosen large such asin the order of 200-ms or 320-ms.

Comparing the three options, the third option allows a more dynamicresource reconfiguration (which is not possible with the first optionsince RRC configuration incurs large delay) without incurring large DLsignaling overhead (which is the case with the second option).Therefore, it allows a more efficient pooling of Ap-CSI-RS resourceswith reasonable DL signaling overhead. To set up a UE for the thirdoption, an RRC configuration similar to the one for SPS-ConfigDL (TS36.331, REF5) can be used. Only a few parameters are applicable (forexample, parameters similar to semiPersistSchedIntervalDL and/ornumberOfConfSPS-Processes).

Considering the aforementioned three signaling options, applicable toeach of the three parameters, TABLE 1-A and 1-B describe severalpossible combinations for the first and the second options of portsubset selection, respectively.

TABLE 1-A Options for DL signaling mechanism of CSI-RS resourceconfiguration with fixed port subset selection (Alt 1) Signalingmechanism Alt No. antenna ports N_(PORT) T-F pattern configuration 1.1RRC signaling (semi-static) RRC signaling (semi-static) 1.2 RRCsignaling (semi-static) Every UL grant which carries A-CSI request(dynamic) 1.3 RRC signaling (semi-static) In one UL grant which carriesA-CSI request (dynamic, semi- persistent) per X ms (X = CSI-RS resourcereconfiguration periodicity) 2.2 Every UL grant which carries Every ULgrant which carries A-CSI request (dynamic) A-CSI request (dynamic) 3.3In one DL assignment or UL In one DL assignment or UL grant whichcarries A-CSI grant which carries A-CSI request (dynamic, semi- request(dynamic, semi- persistent), e.g. per X ms persistent), e.g. per X ms (X= CSI-RS resource (X = CSI-RS resource reconfiguration periodicity)reconfiguration periodicity) or aperiodically or aperiodically

TABLE 1-b Options for DL signaling mechanism of CSI-RS resourceconfiguration with flexible port subset selection (Alt 2) Signalingmechanism       Alt       No. antenna ports N_(PORT)       T-F patternconfiguration $\quad\begin{matrix}{{Port}\mspace{14mu} {subset}} \\\begin{Bmatrix}{{{Port}(0)},{{Port}(1)},\ldots \mspace{14mu},} \\{{Port}\left( {N_{PORT} - 1} \right)}\end{Bmatrix}\end{matrix}$ 1.1.1 RRC signaling (semi- RRC signaling (semi-static) RRCsignaling (semi-static) static) 1.1.2 RRC signaling (semi- RRC signaling(semi-static) Every UL grant which static) carries A-CSI request(dynamic) 1.1.3 RRC signaling (semi- RRC signaling (semi-static) In oneDL assignment or static) UL grant which carries A- CSI request (dynamic,semi-persistent), e.g. per X ms (X = CSI-RS resource reconfigurationperiodicity) or aperiodically 1.2.1 RRC signaling (semi- Every UL grantwhich RRC signaling (semi-static) static) carries A-CSI request(dynamic) 1.3.1 RRC signaling (semi- In one DL assignment or RRCsignaling (semi-static) static) UL grant which carries A- CSI request(dynamic, semi-persistent), e.g. per X ms (X = CSI-RS resourcereconfiguration periodicity) or aperiodically 1.2.2 RRC signaling (semi-Every UL grant which Every UL grant which static) carries A-CSI requestcarries A-CSI request (dynamic) (dynamic) 1.3.3 RRC signaling (semi- Inone DL assignment or In one DL assignment or static) UL grant whichcarries A- UL grant which carries A- CSI request (dynamic, CSI request(dynamic, semi-persistent), e.g. per X semi-persistent), e.g. per X ms(X = CSI-RS resource ms (X = CSI-RS resource reconfigurationperiodicity) reconfiguration periodicity) or aperiodically oraperiodically 2.2.2 Every UL grant which Every UL grant which Every ULgrant which carries A-CSI request carries A-CSI request carries A-CSIrequest (dynamic) (dynamic) (dynamic) 3.3.3 In one DL assignment or Inone DL assignment or In one DL assignment or UL grant which carries ULgrant which carries A- UL grant which carries A- A-CSI request (dynamic,CSI request (dynamic, CSI request (dynamic, semi-persistent), e.g. persemi-persistent), e.g. per X semi-persistent), e.g. per X X ms (X =CSI-RS ms (X = CSI-RS resource ms (X = CSI-RS resource resourcereconfiguration reconfiguration periodicity) reconfigurationperiodicity) periodicity) or or aperiodically or aperiodicallyaperiodically

For each of the options in TABLE 1-A and 1-B, at least a CSI requestfield in the DCI of an UL grant (which includes an associated aperiodicCSI-RS) is needed to trigger A-CSI. The CSI request field can includeone or multiple bits where each bit is associated with a cell. Inaddition, Ap-CSI-RS parameter(s) which need to be configured dynamically(a subset of the number of ports, T-F pattern configuration, and/or portsubset) are also included in the DCI of the UL grant. Theseconfiguration parameters can be defined as separate parameters orjointly with the CSI request field.

When a UE is configured with K CSI-RS resources (or resourceconfigurations), one CSI request field (which can include one ormultiple bits) can be used for each of the K CSI-RS resources (orresource configurations). When k of these K CSI request fields are setto 1, CSI-RS associated with each of these k CSI-RS resources (orresource configurations) is transmitted in the DL subframe containingthe UL grant.

When a UE is configured with two (possibly different) CSI reporting(analogous to LTE eMIMO-Type) setups or CSI-RS levels within one CSIprocess where each eMIMO-Type setup is associated with one or moreCSI-RS resources (or resource configurations), one CSI request field(which can include one or multiple bits) can be used for each of the twoeMIMO-Type setups. When either one or both CSI request fields are set to1, CSI-RS associated with each triggered eMIMO-Type setup is transmittedin the DL subframe containing the UL grant.

When a combination of semi-static (RRC signaling) and eithersemi-persistent or dynamic signaling is used (such as Alt 1.1, 1.2, or1.3 in TABLE 1-A; Alt 1.1.1, 1.1.2, 1.1.3, 1.2.1, 1.3.1, 1.2.2, or 1.3.3in TABLE 1-B), at least one (non-zero-power NZP or zero-power ZP) CSI-RSresource configuration parameter is semi-statically configured and atleast one CSI-RS resource configuration parameter is eithersemi-persistently or dynamically configured. In this case, thesemi-static CSI-RS resource configuration effectively indicates that theUE is semi-statically configured with a plurality of (K_(A)) CSI-RSresources (where K_(A) is the number of possible CSI-RS resources orresource configurations associated with the semi-statically configuredparameters). The second signaling—either semi-persistent ordynamic—selects one CSI-RS resource or a subset of CSI-RS resources fromthe K_(A) semi-statically configured CSI-RS resources. Therefore,instead of defining CSI-RS resources in terms of parameters, thesemi-static (higher-layer or RRC) signaling can instead configure the UEa set of K_(A) CSI-RS resources and the semi-persistent or dynamicsignaling can select one of out of K_(A) CSI-RS resources. Each of theseCSI-RS resources can either be NZP or ZP.

In the present disclosure, several embodiments of CSI-RS resource(re)configuration scheme (referred above as semi-persistent resourcereconfiguration) with at least one CSI-RS resource configurationparameter signaled using the third option are given.

In a first embodiment (embodiment 1.A), anactivation-release/deactivation mechanism similar to semi-persistentscheduling is utilized to reconfigure CSI-RS resource. In thisembodiment, UL grants or DL assignments on L1 DL control channels(analogous to LTE PDCCH or EPDCCH) are used to reconfigure CSI-RSresource. Therefore, an UL grant or DL assignment used for this purposeincludes at least one DCI field either for selecting one out of multiplechoices of CSI-RS resource configuration (which are, for instance,configured via higher layer signaling as a part of CSI-RS resourceconfiguration ASN.1 Information Element) or for setting the value of atleast one CSI-RS resource configuration parameter. This field can be apart of an existing DCI format (such as that analogous to LTE DCI format0 or 4 for UL grant, or format 1A, 2/2A/2B for DL assignment) or a newDCI format specifically designed for CSI-RS resource reconfiguration(activation/deactivation). The UL grant (or DL assignment) is signaledto the UE via PDCCH or EPDCCH and masked by a special RNTI (such asCSI-RNTI).

FIG. 11 illustrates example eNB and UE operations in terms of timingdiagram 1100 associated with eNB in 1101 and UE in 1102 wherein at leastone CSI-RS resource configuration parameter is signaled using the thirdoption according to embodiments of this disclosure. For example, thiscorresponds to Alt 1.3 or 3.3 in TABLE 1-A, or Alt 1.1.3, 1.3.1, 1.3.3,or 3.3.3 in TABLE 1-B. In this embodiment, Ap-CSI-RS resource isreconfigured every X ms in subframe(s) 1110 via an UL grant (or anUL-related grant or, alternatively, a DL assignment) which carriesAp-CSI-RS resource configuration information (including the DCI fieldmentioned above). This configuration information can be accompanied withan A-CSI request/trigger or signaled by itself. Upon receiving a DLsubframe from 1110, a served UE-k reads the configuration information in1130. Based on this configuration information, the eNB requests A-CSI toUE-k via an UL grant (containing A-CSI trigger) while transmittingAp-CSI-RS within the same subframe(s) 1120. Upon receiving a DL subframefrom 1140—containing an A-CSI request/trigger—UE-k measures thetransmitted Ap-CSI-RS (in subframe n) according to the resourceconfiguration information received in subframe(s) 1130, and performs CSIcalculation. The resulting A-CSI is reported to the eNB in subframe(s)1150. In the example in FIG. 11, the semi-persistently configured CSI-RSresource includes a set of the number of ports.

Although the above example assumes periodic resource reconfiguration(every X ms), aperiodic resource reconfiguration using activation anddeactivation based on UL grant or DL assignment can also be used.

The above semi-persistent CSI-RS resource allocation mechanism, appliedto NZP CSI-RS resource, can be described as follows. First, a UEreceives a dynamic trigger/release containing a selection from multiplehigher-layer-configured NZP CSI-RS resources. These multiple CSI-RSresources can be associated with a first set of configured parameters(set values of CSI-RS resource configuration parameters) or simply alist of K_(A) CSI-RS resources. Likewise, dynamic trigger or release canindicate either a ┌log(K_(A))┐-bit DCI field or another set ofparameters which, together with the first parameter set, furtherindicates the selected CSI-RS resource. In this embodiment, each NZPCSI-RS resource can be either periodic or aperiodic CSI-RS resource.Second, for an activation trigger received in subframe n, thetransmission of the associated NZP CSI-RS resource will start no earlierthan subframe n+Y1 where Y1>0. Third, for a release (deactivation)trigger received in subframe n, the transmission of the associated NZPCSI-RS resource will stop after subframe n+Y1 where Y1>0. Fourth, if anUL grant or UL grant-like mechanism is used to trigger CSI-RS which isplaced or transmitted in a same subframe as the UL grant, the value ofY1 or Y2 can be aligned with that of A-CSI. The same holds if a DL grantis used instead.

In a second embodiment (embodiment 1.B), anactivation-release/deactivation mechanism (similar to semi-persistentscheduling) is also utilized to reconfigure CSI-RS resource, but insteadof using PDCCH, MAC control element (MAC CE) is used. Here, a new typeof MAC CE can be defined for the purpose of reconfiguring CSI-RSresource. For example, this type of MAC CE can be termed “CSI-RSresource reconfiguration MAC control element (MAC CE)”.

This CSI-RS resource reconfiguration MAC CE is signaled to the UE viaDL-SCH and included in a MAC PDU. Since the number of CSI-RS resourceconfiguration parameters (as well as the length of each parameter)included in the MAC CE remains the same, the size of CSI-RS resourcereconfiguration MAC CE can be fixed. An example of a MAC CE design forCSI-RS resource reconfiguration includes at least one CSI-RS resourceconfiguration parameter, each written as a binary (bit) sequence andarranged in an octet-aligned format. For instance, if all the threeparameters mentioned above (number of ports, T-F pattern, and portnumber set) are configurable via a MAC CE, three fields are included inthe CSI-RS resource configuration MAC CE.

The above semi-persistent CSI-RS resource allocation schemes (the firstand the second embodiments) can also be used for zero-power (ZP) CSI-RSresource which can be used for interference measurement.

The above semi-persistent CSI-RS resource allocation schemes (the firstand the second embodiments are used and applicable for aperiodic CSI-RS.In another example, these first and the second embodiments can also beapplied to periodic CSI-RS (that which is associated with subframeconfiguration in CSI-RS resource configuration—such as subframe offsetand periodicity). When applied to periodic CSI-RS, each of the twoschemes can be used to start/activate or stop/deactivate CSI-RSmeasurement at a UE. For the first embodiment, a DCI field in an ULgrant or a DL assignment is used to signal the start or the stop of CSImeasurement associated with a selected CSI-RS resource. For the secondembodiment, the CSI-RS resource reconfiguration MAC CE is used to signalthe start or the stop of CSI measurement associated with a selectedCSI-RS resource.

For either embodiment, two possibilities exist. First, the size andcontent of the DCI field (first embodiment) or MAC CE (secondembodiment) can be different from that used for aperiodic CSI-RS. Inthis case, the selected CSI-RS resource is configured for the UE viahigher layer signaling. Therefore, the DCI field (first embodiment) orthe MAC CE (second embodiment) simply signals START (activate) or STOP(deactivate). Second, the size and content of the DCI field (firstembodiment) or MAC CE (second embodiment) are identical to that used foraperiodic CSI-RS. In this case, the selected CSI-RS resource isindicated in the DCI field (first embodiment) or the MAC CE (secondembodiment)—selected out of a plurality of (K_(A)) resources which areconfigured for the UE via higher-layer signaling—in the same manner asthat for aperiodic CSI-RS.

The above embodiments pertain to CSI-RS design which enables efficientresource allocation mechanism for next generation cellular systems.Additionally, there is a need to enhance the existing synchronizationand cell search procedure for new communication systems such as 5G atleast for the following reasons. First, beamforming support. In order tomeet link budget requirements for operation in high carrier frequencybands, such as ones above 6 GHz, beamforming is required fortransmissions by an eNB (and possibly also by a UE). Therefore, theaforementioned synchronization and cell search procedure (see alsoREF 1) needs to be updated for beamforming support. Second, largebandwidth support. For operation with large system bandwidths, such as100 MHz or above, a different sub-carrier spacing than the one foroperation in the smaller system bandwidths can apply and such designneeds to be considered for the synchronization and cell search proceduredesign. Third, improved coverage. For some applications, such as onesassociated with a requirement for increased coverage that can occur dueto placements of UEs in locations experiencing a large path loss, thesynchronization and cell search procedure needs to support enhancedcoverage and increased repetitions of synchronization signals. Fourth,improved performance. The synchronization performance of theaforementioned procedure (as also described in REF 1) is limited due tofalse alarms caused by the partitioning a cell ID into 1 PSS and 2 SSS,thereby leading to invalid combinations of primary/secondarysynchronization signal (PSS/SSS) that cannot completely resolved byscrambling. A new synchronization procedure can be designed withimproved false alarm performance. Fifth, support for variable TTI. Incurrent LTE Rel-13, the TTI duration is fixed. However, for 5G systems,the TTI is expected to be variable due to support for differentsub-carrier spacings, low latency considerations etc. In this scenariowith variable TTI, the mapping of the synchronization sequences and cellsearch within the frame needs to be specified.

The present disclosure includes at least the following five componentsfor cell search and synchronization signal designs: cell searchprocedure, PSS design, SSS design, primary broadcast channel (PBCH)design, and their associated frame structure.

For the first component (that is, cell search procedure), one embodimentcan be described as follows. In one embodiment of the disclosure, a UEscans for a single symbol or multiple symbol PSS configurationtransmitted by an eNB based on a frequency band pre-configured in theUE. A minimum bandwidth and sub-carrier spacing used by the UE is alsodependent on the frequency band pre-configuration.

FIG. 12 illustrates an example operating procedure 1200 forsynchronization according to embodiments of this disclosure. Frequencyband dependent parameters such as sub-carrier spacing, minimumbandwidth, and PSS configuration are configured based on a frequencyband that a UE scans. Based on the pre-configuration, the radiofrequency (RF) and physical layer parameters, such as the correlator andthe synchronization sequences, are adjusted for synchronization to scanin the frequency band.

For example, when a UE scans for a 28 GHz band (mmWave cellular band),the UE scans for a 4 symbol PSS configuration with a sub-carrier spacingof 75 KHz. When the UE scans in a 3 GHz band (existing cellular band),the UE scans for a single symbol PSS configuration with sub-carrierspacing of 15 KHz. When the UE scans in 700 MHz band (IoT cellularband), the UE scans for multiple symbol PSS configuration withsub-carrier spacing of 3.75 KHz.

In another example, when a UE scans for a 28 GHz band (mmWave cellularband), the UE scans for a 8 symbol PSS configuration with a sub-carrierspacing of 60 KHz. When the UE scans in a 3 GHz band (existing cellularband), the UE scans for a single symbol PSS configuration withsub-carrier spacing of 15 KHz. When the UE scans in 700 MHz band (IoTcellular band), the UE scans for multiple symbol PSS configuration withsub-carrier spacing of 3.75 KHz.

This embodiment also covers examples wherein a plurality of PSSconfigurations is supported and each PSS configuration can be associatedwith at least one class of frequency bands. The PSS configurationincludes (but is not limited to) the number of PSS symbols, sequenceand/or waveform choice and length, location in time and/or frequencydomain, the number of cell-specific hypotheses, or the number ofpossible sequences for PSS.

Another embodiment does not explicitly associate PSS configuration witha frequency band. Instead, it defines a plurality of PSS configurationsets wherein each set includes PSS characteristics such as the number ofPSS symbols, sequence and/or waveform choice and length, location intime and/or frequency domain, the number of cell-specific hypotheses, orthe number of possible sequences for PSS.

For example, SS Type 1 uses a 4-symbol PSS configuration with asub-carrier spacing of 75 KHz. SS type 2 uses a single symbol PSSconfiguration with sub-carrier spacing of 15 KHz. SS type 3 usesmultiple symbol PSS configuration with sub-carrier spacing of 3.75 KHz.

In another embodiment, UE simultaneously examines multiple hypothesesand scans for both multiple symbol PSS and single symbol PSS. This canbe beneficial if there is no pre-configuration for the number ofrepetitions and the UE blindly tries both options for synchronization.

In another embodiment, the synchronization signal transmission can becarrier-agnostic. That is, the same numerology is used for the syncirrespective of the carrier frequency. The sync uses a fixed bandwidthand numerology that is common for all UEs irrespective of carrierfrequency. Even though UEs can support different numerologies andoperate in different bands, they are required to support the detectionof the sync based on this common numerology.

To mitigate sync overhead to support beamforming and to support highspeed scenarios, the default carrier spacing can be different than the15 KHz spacing used in LTE. For example, 30 KHz or 60 KHz spacing couldbe considered as the default numerology for initial access.

For the second component (that is, PSS design), one embodiment can bedescribed as follows. In one embodiment of the present disclosure, bothsingle symbol and multiple symbol PSS transmissions are supported. Anumber of sequences available for the PSS transmission is denoted by P.Each symbol in the PSS configuration is used to transmit a different PSSsequence, derived from a different root u of a ZC sequence. Each PSSsequence S_(i) (1≤i≤P) is a ZC sequence of length N_(ZC) that is theclosest prime number less than the minimum bandwidth supported in agiven frequency band divided by a respective sub-carrier spacing usedfor PSS transmission in the frequency band. Each PSS sequence isconstructed in the frequency domain with a middle element punctured toavoid transmitting on the DC sub-carrier. When PSS transmission is overmultiple symbols, the multiple PSS transmissions are in contiguousadjacent symbols. Each repetition of a multi-symbol PSS transmission canbe in a same direction, that is with a same precoding (repetitions canbe for coverage enhancements or to enable per-UE beamforming) or indifferent directions using different precoding (for eNB beamforming).

FIG. 13 illustrates an example PSS transmission scheme 1300 applied overa single symbol (P=1) and over multiple symbols (P>1) according toembodiments of this disclosure. A single symbol PSS transmission 1301using sub-carrier spacing f_(SC,1) occupies bandwidthBW1=N_(ZC)×f_(SC,1) and time T₁. A multiple symbol PSS transmission 1302using sub-carrier spacing f_(SC,2) occupies bandwidthBW2=N_(ZC)×f_(SC,2) and time PxT₂.

In one embodiment of this disclosure, PSS sequences are transmitted ascomplex conjugate pairs to eliminate timing ambiguity from integerfrequency offsets. For example, when P=4 and N_(ZC)=63, PSS sequencescan be based on the root indices u={34, 29, 25, 38}.

In case of single symbol PSS transmission, each cell can select one ofthe available P sequences. For example, when PSS set is based on theroot indices u={34, 29, 25, 38}, each cell can select of the P=4sequences. For example, when cell 1 transmits PSS based on root index{34}, cell 2 can transmit PSS based on root index {29}. Only ┌P/2┐correlators are required due to the complex conjugate property of ZCsequences chosen for PSS, where ┌┐ is the ceiling function that rounds anumber to its next larger integer.

FIG. 14A illustrates an example of a single symbol PSS transmission frommultiple cells where the UE receives different PSS from neighboringcells in a wireless network 1400 according to embodiments of thisdisclosure. The figure shows the UE 1404 receiving different PSStransmissions {S_(i), S_(j), S_(k)} from cells 1401, 1402 and 1403respectively, where 1≤i, j, k≤P and i≠j≠k.

At the UE, multiple correlators are used to detect the PSS from currentand neighboring cells. In one example, a UE has 2 correlators, one foru={34, 29} and another for u={25, 38}. Correlator 1 detects PSStransmission from cell 1 while correlator 2 detects PSS transmissionfrom cell 2. This approach can mitigate the SFN effect that can occurwhen all cells transmit a same PSS sequence, making it difficult toestimate the timing when the correlator output exceeds the CP length.

In case of multiple symbol PSS transmission, each cell can transmit allP sequences S₁, S₂, . . . , S_(P). The PSS transmissions over multiplesymbols can have a different precoding per symbol or can have a sameprecoding. Since each repetition uses a different PSS sequence, a UE candetermine the position of the PSS repetition within a sub-frame based onthe PSS sequence the UE detects for synchronization.

A different precoding is used per symbol in a beamforming mode. In thiscase, a PSS transmission sequence can be rotated in adjacent cells. A UEscans in parallel for multiple symbols using separate correlators. Therotation can be such that different correlators are triggered at the UEwhen the UE receives multiple PSS sequences from a current cell as wellas from neighboring cells.

FIG. 14B illustrates an example for multiple symbol transmission withthe PSS sequences being rotated for multiple cells to minimizetriggering the same correlator for the transmission from the neighboringcells in a wireless network 1450 according to embodiments of thisdisclosure. Cell 1 1451 transmits PSS using sequences {S₁, S₂, . . . ,S_(P)} to the UE 1454. Cell 2 1452 transmits {S_(i), S_(i+1), . . . ,S_(P), S₁, . . . , S_(i−1)} which triggers a different correlator forthe UE 1454. Cell 3 1453 transmits {S_(j), S_(j+1), . . . , S_(P), S₁, .. . , S_(j−1)} which triggers yet another correlator for the UE 1454.Hence, the SFN effect is not seen and the UE 604 can easily distinguishthe transmissions from the different cells.

For example, when 4 symbols are used for a PSS transmission and cell 1transmits PSS based on root indices u={34, 29, 25, 38}, cell 2 cantransmit based on root indices {25, 38, 34, 29}. Assuming UE has 2correlators, one for u={34, 29} and another for u={25, 38}, correlator 1detects PSS transmission from cell 1 while correlator 2 detects PSStransmission from cell 2. This mitigates the SFN effect due to multiplerepetitions when all cells transmit a same sequence leading to ambiguityin both the repetitions from the current cell as well as thetransmissions from the neighboring cell. A UE can assume that a sameprecoding and repetition pattern applies to other broadcast signals suchas SSS and PBCH. This enables support for beamforming from the eNB.

A same precoding for all PSS transmission symbols can be used in acoverage enhancement mode. In this case, a UE receiver can use a singlelong correlator to correlate across multiple symbols and obtain aprocessing gain needed for enhanced coverage. The SFN effect is not anissue since UEs are coverage limited (not interference limited) in thismode. Alternate structures with smaller correlators can also be used forreduced complexity considerations when frequency error is small andcorrelator outputs can be combined for achieving the desired processinggain.

FIG. 15 illustrates different options for PSS transmission design forsingle and multiple symbol PSS configuration, according to embodimentsof this disclosure. The P symbols used for PSS transmission are denotedby {S₁, S₂, . . . , S_(P)}.

PSS transmissions including a combination of precoding and repetition isalso possible to support UE beamforming for synchronization. This can bedone in multiple ways. In one method, each precoding is repeated M timesbefore switching to the next beam. In this case, the transmissions canbe {S₁, S₁, S₁, . . . M times, S₂, S₂, S₂, . . . , S_(P)} requiring P*Mtransmissions. In this scheme, the UE continuously switches its beam P*Mtimes while the eNB holds its beam for M symbols. In another method, thetransmissions can be {S₁, S₂, . . . S_(P), S₁, S₂, . . . , S_(P), S₁,S₂, . . . , S_(P), . . . . M times}. In this case, the UE holds itscurrent beam for P symbols before switching to another beam while theeNB is continuously switching its beam.

In order to distinguish between normal CP and extended CP and todistinguish between FDD and TDD operation, different locations within aframe can be used for the PSS transmission symbols. A UE can performblind detection for hypotheses derived from the possible combinations inorder to determine a combination, such as FDD and normal CP, used forPSS transmission.

In one embodiment of this disclosure, the PSS is used only for coarsesynchronization and a SSS provides a cell ID.

The above embodiments utilize multiple-symbol configuration to lengthenor extend the PSS and therefore introduce time diversity. In anotherembodiment, this PSS extension operation is performed in frequencydomain. FIGS. 16A-16C illustrate examples where the PSS is extended inthe frequency domain according to embodiments of this disclosure. Thatis, a PSS can be composed of P segments of RE groups, whether adjacentas shown in FIG. 16A or distributed in frequency domain as shown in FIG.16B, where different segments carry different frequency domain ZCsequences. Each segment uses bandwidth BW3=N_(ZC)×f_(SC,1) wheref_(SC,1) is the sub-carrier spacing. In this case, N_(ZC) is not derivedfrom the minimum bandwidth but is fixed to a pre-determined value.Hybrid designs could also be considered where a portion of the PSSextension is done in the time domain while another portion is done inthe frequency domain, as shown in FIG. 16C. This could be useful toconcentrate the power in the time domain into fewer resources whileminimizing overhead for multiple repetitions.

Yet another embodiment is to perform PSS extension both in time andfrequency domains. Here the P segments occupy P symbols and differentPSS segments are placed at different RE groups according to apredetermined hopping pattern. FIG. 16D illustrates an example where theUE scans for the PSS extensions in different RE groups, based on a knownhopping pattern within the specified bandwidth, for example, afterdetecting a first PSS symbol S₁ at a predetermined location according toembodiments of this disclosure. Using a plurality of hopping patternscan increase the number of cell-specific hypotheses (such as partial PCIor other cell-specific parameters).

The use of ZC sequences in the above embodiments is exemplary. Othersequences based on sequence group with good auto-correlation andcross-correlation property, such as M-sequences or Golay codes, can alsobe used. The sequence can be inserted either in time or frequencydomain.

For the third component (that is, SSS design), one embodiment can bedescribed as follows. In one embodiment, both single and multiple symbolSSS transmissions are supported. SSS sequences are generated usingmaximum length sequences, also known as M-sequences of length M. A SSSsequence is constructed in the frequency domain. A SSS transmission usesa same sub-carrier spacing and bandwidth as a PSS transmission. In thecase of multiple symbol SSS transmission, a number of repetitions and aprecoding operation (beamforming or no beamforming) of the SSStransmission are also same as for a PSS transmission. Each cell uses adifferent SSS sequence that provides a respective Cell ID. Unlike a PSSsequence, a SSS sequence does not change during repetitions for coverageor for beamforming.

FIG. 17 illustrates an example SSS transmission for single and multiplesymbol transmission according to embodiments of this disclosure. For thefourth component (that is, PBCH design), one embodiment can be describedas follows. In one embodiment, a UE does not know whether or not an eNBapplies beamforming until the UE decodes a PBCH. The PBCH transmissionalso uses a same sub-carrier spacing, and precoding operation as the PSSand SSS transmissions.

Information on a symbol offset from a first PSS/SSS transmission can beencoded in a master information block (MIB) conveyed by the PBCH for aUE to confirm a symbol timing within the sub-frame for multiplerepetitions of the PBCH transmission. This can be useful in cases wheremultiple symbols were detected for the PSS and SSS during a multiplesymbol transmission and the UE wants to confirm that it has estimatedthe symbol timing index within the sub-frame correctly.

FIG. 18 illustrates an example where a symbol offset information isincluded, as shown by a variable Indx, in a Master Information Block(MIB) transmitted via PBCH according to embodiments of this disclosure.

A UE decodes contents of a MIB in a PBCH and confirms its symbolposition among symbol positions for a transmission with multiplerepetitions. Once a UE detects a MIB in PBCH transmission, the UE caninitiate unicast data and control channel transmission or receptionbased on a scheduling configuration by the eNB.

For the fifth component (that is, associated frame structure), oneembodiment can be described as follows. In case of single symbol PSS/SSStransmission, in one embodiment of this disclosure, the eNB transmitsthe PSS as a last symbol of a sub-frame and the eNB transmits the SSS asthe first symbol of the next sub-frame. The eNB then transmits the PBCHon the subsequent subframe. Sending the PSS in the last slot helps withacquiring the PSS independent of whether a normal CP or extended CP isused. Also, using 2^(nd) slot in the sub-frame allows the PSS, SSS, PBCHto be repeated across the sub-frame for multiple symbol transmissions,if desired. The first PSS transmission always occurs at sub-frame #0.The PSS and SSS are repeated exactly 5 msec apart in the frameirrespective of the TTI duration.

FIG. 19A illustrates an example frame structure 1900 that shows theplacement of the PSS, SSS and PBCH for a single symbol transmissionaccording to embodiments of this disclosure. The second repetition ofthe SSS is inverted so that the UE can determine the location andrepetition in the frame from a single observation of the SSS. If thereare K sub-frames per 10 msec frame, PSS is sent at sub-frame SF #0 andSF # K/2−1, where sub-frame SF #0 denotes the start of the frame.

In case of multiple symbol PSS/SSS transmission, in one embodiment ofthis disclosure, the PSS sequences are transmitted sequentially inreverse order starting from a last symbol of a sub-frame while the SSSrepetitions are transmitted sequentially starting from the first symbolof the next sub-frame. The PBCH repetitions is then transmitted on thesubsequent subframe. If precoding is applied, the same precoder isapplied for each PSS, SSS, PBCH transmission.

FIG. 19B illustrates an example frame structure 1920 that shows theplacement of the PSS, SSS and PBCH for a multiple symbol transmissionaccording to embodiments of this disclosure.

In another embodiment, there exist scenarios where there is sufficientbandwidth such as in mmWave frequency bands but there is a need toreduce the time overhead for multiple symbol transmission. In suchcases, FDM of PSS/SSS/PBCH can be considered. This design also supportsbeamforming since the same precoding is applied to the correspondingsymbols for PSS, SSS and PBCH. FIG. 19C illustrates an example framestructure 1940 where the PSS, SSS and PBCH are frequency divisionmultiplexed. In this case, it makes sense to repeat the PBCH forsubsequent transmissions within the frame to keep the total power andbandwidth constant for the transmissions in contrast to the TDM approachpresented in this disclosure where the PBCH is transmitted only once perframe. An inverted SSS sequence can still be utilized to indicate theposition of the repetition within the frame.

In another embodiment, although multiple numerologies can be supportedat the eNB, only a single synchronization signal of a predeterminednumerology and using pre-determined resources and periodicity istransmitted by the eNB in a given frequency band. The design of thesynchronization signal parameters such as bandwidth and the sequencedesign can be frequency band specific. An example of frequency bandspecific synchronization signal numerology is shown in TABLE 2. A UE isconfigured to only search for a single synchronization signal of apre-determined numerology in a given frequency band at a given time.

TABLE 2 Sync Number Beam- Sub- Carrier signal sub- of repeti- formingframes Sub- fre- carrier tions in a support per frame quency spacingsubframe at eNB frame location 800 MHz 3.75 KHz 8 N/A 10 #1, #5 2 GHz 15KHz 1 N/A 10 #1, #5 28 GHz 60 KHz 14 yes 100  #1, #50 70 GHz 120 KHz 14yes 200  #1, #100

In one embodiment, to avoid SFN effect, PSS/SSS can be designed with adifferent (longer) CP length which accommodates SFN effect associatedwith most scenarios. For instance, the longest CP length available canbe used for PSS/SSS. Thus, use of multiple PSS can be avoided. The PBCHcan utilize a similar structure.

In one embodiment of the present disclosure, the PSS transmissionswithin a frame are structured into 2 groups. Group 1: PSS transmissionsare made to support eNB and UE beamforming. Group 2: Repetition of group1 after a specific time interval (5 ms, for example) which is used forcoarse timing acquisition, frequency offset estimation and correction.

FIG. 20A illustrates an example where PSS transmission is repeatedaccording to embodiments of this disclosure. A first group of PSStransmissions is made where the PSS transmissions are beamformed for Psymbols and then repeated to support UE beamforming after time intervalT1. This repetition could be contiguous to the first set (i.e. T1=P, forexample). There can be M repetitions of P PSS transmissions within thefirst group (M>1 to support UE beamforming). The entire group oftransmissions is then repeated within a frame at time instant T2 toestimate the coarse timing and frequency offset. T2>>T1 to provideaccurate frequency offset for the sync within the frame (T2=5 ms, forexample).

The order of eNB and UE beamforming can also be reversed as illustratedin FIG. 20B. A first group of PSS transmissions is made where the PSStransmissions are repeated for M symbols to support UE beamforming andthen the eNB changes its beam after time interval T1 P times within thefirst group. This repetition could be contiguous to the first set (i.e.T1=M, for example, and M>1 to support UE beamforming). The entire groupof transmissions is then repeated within a frame at time instant T2 toestimate the coarse timing and frequency offset. T2>>T1 to provideaccurate frequency offset for the sync within the frame (T2=5 ms, forexample).

FIG. 21 illustrates a flowchart for an example method 2100 wherein a UEreceives RS resource configuration information and at least two RS2according to an embodiment of the present disclosure. For example, themethod 2100 can be performed by the UE 116.

The method 2100 begins with the UE receiving RS resource configurationinformation (step 2101) and at least two RSs (step 2102), wherein afirst RS RS1 is non-UE-specifically configured and a second RS RS2 isUE-specifically configured. For example, the non-UE-specificallyconfigured RS is a RS that is not configured for a specific UE, butrather may be generally applicable to multiple different UEs. In otherwords, the non-UE-specifically configured RS may be generated andtransmitted by an eNB to be measured by multiple different UEs.Additionally, for example, the UE-specifically configured RS is a RSthat is configured for a specific UE, such as, configured for UE 116. Inother words, the UE-specifically configured RS may be generated andtransmitted by an eNB to be measured by a particular UE, such as, UE116.

Once the RSs are received, the UE measures at least one of the RSs (step2102). The first RS RS1, non-UE-specifically configured, can be eithercell, UE-group, or transmit-receive-point (TRP) specifically configured.Therefore, at least some configuration information about RS1 is receivedvia a broadcast channel. In addition, the first RS can include K>1CSI-RS resources. For the second RS RS2, used thereafter to calculateand derive CSI (step 2103), at least some configuration informationabout RS2 via higher-layer signaling. The calculated CSI is thenreported by transmitting it on an uplink channel (step 2104).

Although RS1 is non-UE-specific and RS2 UE-specific, time-frequencypatterns associated with RS1 is a subset of time-frequency patternsassociated with RS2. Furthermore, a third RS RS3, distinct from RS2, canbe further configured as a UE-specific RS.

FIG. 22 illustrates a flowchart for an example method wherein a BSconfigures a UE (labeled as UE-k) with RS resources according to anembodiment of the present disclosure. For example, the method 2200 canbe performed by the eNB 102.

The method 2200 begins with the BS configuring UE-k with RS resources(step 2201). This information is included in RS resource configurationinformation. The BS further transmits at least two RSs (step 2202),wherein a first RS RS1 is non-UE-specifically configured and a second RSRS2 is UE-specifically configured. The first RS RS1, non-UE-specificallyconfigured, can be either cell, UE-group, or transmit-receive-point(TRP) specifically configured. Therefore, at least some configurationinformation about RS1 is received via a broadcast channel. In addition,the first RS can include K>1 CSI-RS resources. For the second RS RS2,used thereafter to calculate and derive CSI by UE-k, at least someconfiguration information about RS2 via higher-layer signaling. The BSfurther receives CSI reporting from UE-k, derived from measuring RS2, onan uplink channel (step 2203).

Although RS1 is non-UE-specific and RS2 UE-specific, time-frequencypatterns associated with RS1 is a subset of time-frequency patternsassociated with RS2. Furthermore, a third RS RS3, distinct from RS2, canbe further configured as a UE-specific RS.

Although FIGS. 21 and 22 illustrate examples of methods for receivingconfiguration information and configuring a UE, respectively, variouschanges could be made to FIGS. 21 and 22. For example, while shown as aseries of steps, various steps in each figure could overlap, occur inparallel, occur in a different order, occur multiple times, or not beperformed in one or more embodiments.

Although the present disclosure has been described with an exampleembodiments, various changes and modifications can be suggested by or toone skilled in the art. It is intended that the present disclosureencompass such changes and modifications as fall within the scope of theappended claims.

What is claimed:
 1. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver configured to: receive firstinformation regarding a configuration of at least one semi-persistentchannel state information-reference signal (CSI-RS) resource; receivesecond information for activating the at least one semi-persistentCSI-RS resource; and receive at least one CSI-RS through the at leastone semi-persistent CSI-RS resource; and a processor operably connectedto the transceiver, the processor configured to determine CSI based onthe at least one CSI-RS, wherein the transceiver is further configuredto: transmit the CSI; and receive third information for deactivating theat least one semi-persistent CSI-RS resource.
 2. The UE of claim 1,wherein the second information comprises a media access control (MAC)control element (CE) for activating the at least one semi-persistentCSI-RS resource.
 3. The UE of claim 2, wherein the MAC CE comprises abit sequence arranged in an octet-aligned format.
 4. The UE of claim 1,wherein the second information comprises information indicating the atleast one semi-persistent CSI-RS resource.
 5. The UE of claim 1, whereinthe at least one semi-persistent CSI-RS resource comprises a CSI RSresource for interference measurement.
 6. The UE of claim 1, wherein theCSI is transmitted based on aperiodic CSI reporting.
 7. A base station(BS) in a wireless communication system, the BS comprising: a processor;and a transceiver operably connected to the processor, the transceiverconfigured to: transmit first information regarding a configuration ofat least one semi-persistent channel state information-reference signal(CSI-RS) resource; transmit second information for activating the atleast one semi-persistent CSI-RS resource; transmit at least one CSI-RSthrough the at least one semi-persistent CSI-RS resource; receive CSIthat is based on the at least one CSI-RS; and transmit third informationfor deactivating the at least one semi-persistent CSI-RS resource. 8.The BS of claim 7, wherein the second information comprises a mediaaccess control (MAC) control element (CE) for activating the at leastone semi-persistent CSI-RS resource.
 9. The BS of claim 8, wherein theMAC CE comprises a bit sequence arranged in an octet-aligned format. 10.The BS of claim 7, wherein the second information comprises informationindicating the at least one semi-persistent CSI-RS resource.
 11. The BSof claim 7, wherein the at least one semi-persistent CSI-RS resourcecomprises a CSI RS resource for interference measurement.
 12. The BS ofclaim 7, wherein the CSI is transmitted based on aperiodic CSIreporting.
 13. A method for operating a user equipment (UE) in awireless communication system, the method comprising: receiving firstinformation regarding a configuration of at least one semi-persistentchannel state information-reference signal (CSI-RS) resource; receivingsecond information for activating the at least one semi-persistentCSI-RS resource; receiving at least one CSI-RS through the at least onesemi-persistent CSI-RS resource; determining CSI based on the at leastone CSI-RS; transmitting the CSI; and receiving third information fordeactivating the at least one semi-persistent CSI-RS resource.
 14. Themethod of claim 13, wherein the second information comprises a mediaaccess control (MAC) control element (CE) for activating the at leastone semi-persistent CSI-RS resource.
 15. The method of claim 14, whereinthe MAC CE comprises a bit sequence arranged in an octet-aligned format.16. The method of claim 13, wherein the second information comprisesinformation indicating the at least one semi-persistent CSI-RS resource.17. The method of claim 13, wherein the at least one semi-persistentCSI-RS resource comprises a CSI RS resource for interferencemeasurement.
 18. The method of claim 13, wherein the CSI is transmittedbased on aperiodic CSI reporting.